Japan's Shinya Yamanaka shared this year's Nobel Prize in Physiology or Medicine for his groundbreaking work on producing induced pluripotent stem cells.
Here, in question and answer format, we explain what all the fuss is about.
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Question: What is an iPS cell?
Answer: The word "pluripotent" means that a cell can develop into various cells that make up the body, such as skin, the heart and nerves. A pluripotent cell is called a stem cell.
Q: So, what Yamanaka did was to produce a stem cell artificially?
A: Yes. There are various stem cells in the body. A hematopoietic stem cell, which is in bone marrow, can grow into a white blood cell or a red blood cell. A mesenchymal stem cell can change into blood vessels, heart muscle or fat. There is only kind of cell that can develop into all types of cells.
Q: What is it?
A: It is a fertilized egg, or a cell created when the egg combines with sperm. A human body consists of 60 trillion cells, of more than 200 types, all deriving from a fertilized egg. A fertilized egg is, therefore, called "versatile."
Q: So, a fertilized egg is on a higher level than stem cells?
A: A fertilized egg changing into different cells can be compared to a ball rolling down a mountain. A fertilized egg stands at the top of the mountain, so to speak. It is divided into different groups of cells, such as those related to nerves or those related to blood and muscle. The process can be compared to rain falling on a mountain that flows into different valleys because of ridges and so forth. These intermediate cells eventually become skin, muscle and other cells with a specific function.
Q: Are these solely one-way changes?
A: Look at it this way. A hematopoietic stem cell never becomes a liver cell. It is the same as rain that entered a valley. The rain never crosses a ridge and flows into a different valley. A cell also loses the ability to change into different cells once it is given a specific function. It was long thought that a skin cell could never return to a stem cell or that a stem cell could not regain the "versatility" of a fertilized egg.
Q: But an IPS cell is different?
A: When some genes are introduced, a skin cell, at the foot of the mountain, becomes a cell identical to one in a fertilized egg. Researchers initially could not tell whether the cell returned to the top of the mountain, as it were. This is why the word "pluripotent" was added.
Q: They found the reset button, in other words?
A: If scientists can grow an iPS cell into a nerve cell, for example, it would allow them to restore injured nerves. A heart, a liver and other organs may be able to be created from an iPS cell for treatments that currently require transplants. An egg and sperm of mice have already been produced from iPS cells. The way an iPS cell works is extremely close to a fertilized egg.
Q: It sounds like an iPS cell is almost God-like.
A: At least theoretically, scientists say it is possible to produce an egg and sperm from skin cells and artificially create a life form. The iPS cell technology may change conventional knowledge about life.
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